fast-import --report-fd (Re: fast-import tweaks for remote helpers)

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Jan 5, 2011, 21:20 UTC
Message-ID: <20110105212018.GA22975@burratino>
In-Reply-To: <20101212171633.GB18847@burratino>

Jonathan Nieder wrote:

> Sam Vilain wrote:

Show 5 quoted lines

>> What happened to --report-fd ?
>
> The patch still works.  The main problem with report-fd is that it
> introduced a synchronization point after every commit: the frontend
> has to read the commit id before fast-import will continue.

Correction: more precisely, that was and is the main problem with
svn-fe's use of bidirectional communication.  An application like
Tom's remote helper would probably not suffer so much from it, since
commit ids are just queued up as long as the pipe doesn't fill before
the frontend reads any.  It is transactions like

	FI>	r5 = 734987a9878b97c879c798a897c897ac
	FE>	cat 734987a9878b97c879c798a897c897ac
	FI>	734987a9878b97c879c798a897c897ac commit 448
		tree 8d5bcf0f24bdfea1fdab8d39ba3c8ba91a52547c
		parent 84279592b8b5816d00300ba5d4412adf05cc80d6
		parent 3ca7353cab4ed6c7efac0c8d7477c87112fc7350
		author Junio C Hamano <gitster@pobox.com> 1294187068 -0800
		committer Junio C Hamano <gitster@pobox.com> 1294187068 -0800

		Merge branch 'sr/gitweb-hilite-more' into pu

		* sr/gitweb-hilite-more:
		  gitweb: remove unnecessary test when closing file descriptor
		  gitweb: add extensions to highlight feature map

	FE>	cat 8d5bcf0f24bdfea1fdab8d39ba3c8ba91a52547c "main.c"

(i.e., round-trips) that were and are creating overhead in svn-fe. See [1] if curious about details.

So please don't be dissuaded by the nonsense I sent. :)

[1] http://colabti.org/irclogger/irclogger_log_search/git-devel?search=overhead&action=search